This invention relates to brake systems for bicycles and in particular to such brakes which are operated hydraulically.
A variety of braking systems have been developed over a number of years for use on bicycles with many of these braking systems being mechanical in nature. A common type of braking system for bicycles is the hand operated caliper brake which is movable to engage the sides of the bicycle wheel. The handle to operate this brake can be mounted adjacent the hand grip on the handlebar and the brakes themselves can be connected to the frame structure adjacent the wheel rim. With such brakes, it is common to provide a first braking system to brake the front wheel and a separate but similar braking system to brake the rear wheel. When operating such brakes, it is important that the rear brake be operated prior to or at the same time as the front brake in order to avoid a possibly dangerous braking situation or flipping of the bicycle.
It is also known in this art to provide hydraulically operated braking systems. For example, U.S. Pat. No. 3,993,174 issued Nov. 23, 1976 to Lynn A. Williams et al. describes caliper type bicycle brakes for the front and rear wheels wherein the two brakes are actuated simultaneously by a single actuator assembly mounted adjacent the handlebars. Hydraulic fluid under pressure is delivered to the brakes by two self-contained hydraulic circuits, one for the front brake and one for the rear brake. According to the patent specification, this known brake system has the capability of applying a greater braking force at the front wheel than at the rear wheel. According to the inventors named in the patent specification, their testing has determined that for good braking results, the ratio of braking force should be such that a greater portion of the braking force is applied to the front wheel, contrary to some previous understanding.
More recent U.S. Pat. No. 5,632,362 issued May 27, 1997, teaches a hydraulic operated disc brake for a bicycle. The main unit for this brake system includes a master cylinder, a reservoir housing, and a brake piston housing. This system uses a compensating piston mounted within the reservoir chamber and cooperating with this chamber to define a compensating chamber. This system also includes a master piston shaft with a master piston mounted thereon. The brake piston is reciprocally mounted within the braking piston chamber and the master piston shaft is movable from a braking position to a release position.
A non-hydraulic brake system for a bicycle is taught in U.S. Pat. No. 4,102,439 to Calderazzo. In this unique system, there is a rear wheel brake which can be operated by standard mechanical means including the use of a Bowden cable that extends down from a hand lever mounted on the handlebars. The rear wheel braking torque is the means of actuating the front brakes. Substantial force-amplification characterizes the actuating connection between a rear-wheel torque-reaction pick off and the front brake actuation. The rear wheel braking torque is noted by physical displacement against a spring so that if front wheel brake torque becomes so effective as to substantially reduce rear-wheel brake torque, the spring will automatically react to reduce the magnitude of front brake effort. Although this known braking system has some merit, it appears to suffer from the disadvantages of being relatively complex and therefore relatively expensive to produce and maintain.
It is an object of the present invention to provide an improved hydraulic braking system for a bicycle wherein the operation of the rear brake by the bicycle operator automatically results in an appropriate application of the front brake mechanism as well.
It is a further object of the present invention to provide a hydraulic brake system which is relatively inexpensive to manufacture and install on a bicycle and which is quite easy for a bicycle rider to operate.
According to one aspect of the invention, a bicycle brake system for a bicycle having a frame structure and front and rear wheels includes a rear wheel brake mechanism mountable on the frame structure adjacent the rear wheel, this braking mechanism including a rear wheel braking device for applying a braking force to the rear wheel when the braking device is moved to a rear wheel braking position. The brake system further includes a hydraulic cylinder device mountable on the frame structure adjacent the rear wheel and connected to the rear wheel braking mechanism so as to be actuated thereby when said rear wheel braking device is moved to the rear wheel braking position. There is also a front hydraulic actuator mountable on the frame structure adjacent the front wheel and operatively connected to the hydraulic cylinder device so as to be moved to a front wheel braking position by fluid provided by movement of the hydraulic cylinder device when the hydraulic cylinder device is actuated. A front wheel braking device is connected to the front hydraulic actuator and movable thereby between a non-braking position and a front wheel braking position. During use of the braking system on a bicycle, the front wheel braking device brakes the front wheel when the rear wheel braking device is in the rear wheel braking position and is applying a braking force to the rear wheel. The braking system is constructed to provide a substantially greater braking force on the front wheel compared to the braking force on the rear wheel during all braking conditions of the brake system.
Preferably, the rear wheel braking mechanism includes a hydraulic master cylinder device mountable on the handlebar of the bicycle and a hydraulic cylinder actuator mountable on the frame adjacent the rear wheel and operably connected to the master cylinder device so as to be movable by hydraulic pressure to the rear wheel braking position.
According to another aspect of the present invention, a hydraulic braking system for a bicycle having a frame and a handlebar includes a master hydraulic cylinder mountable on the handlebar of the bicycle and a handle mechanism operably connected to master hydraulic cylinder in order to actuate the master hydraulic cylinder. There is also a first hydraulic cylinder actuator mountable on the frame adjacent said rear wheel and operatively connected to the master hydraulic cylinder so as to be actuated thereby. A rear wheel braking device is connected to the first hydraulic cylinder actuator and operable thereby during use of the brake system. This rear wheel braking device is moved between a disengaged position and a rear wheel braking position. The system further includes a second hydraulic cylinder actuator mountable on the frame adjacent the rear wheel and connected to the rear wheel braking device so as to be operable thereby. This second hydraulic cylinder actuator is movable from an initial position corresponding to the disengaged position of the rear wheel braking device to a secondary position when the rear wheel braking device is in the rear wheel braking position. A third hydraulic cylinder actuator is mountable on the frame adjacent the front wheel and is operably connected to the second hydraulic cylinder actuator so as to be actuated thereby. A front wheel braking device is connected to the third hydraulic cylinder actuator and is operable thereby during use of the brake system. This front wheel braking device is movable between a disengaged position and a front wheel braking position. During use of this brake system, the front wheel braking device brakes a front wheel when the rear wheel braking device is in the rear wheel braking position.
Preferably, the rear wheel braking device includes a rear brake pad and is connected to an outer end of a piston rod which extends from one end of the first hydraulic cylinder actuator. Also the preferred front wheel braking system device includes a front brake pad and is connected to an outer end of another piston rod which extends from one end of the third hydraulic cylinder actuator.
According to a further aspect of the invention, there is provided a brake system in combination with a bicycle having a frame, front and rear wheels rotatably mounted on the frame, and a pivotable handlebar for steering. The braking system of this combination includes a primary brake actuator mounted on the handlebar and including a handle mechanism for manually operating the brake system. There is also a rear wheel braking mechanism including a first hydraulic cylinder actuator mounted on the frame adjacent the rear wheel and operatively connected to the primary brake actuator so as to be actuated by the primary brake actuator during use of the brake system. The rear wheel braking mechanism includes a rear brake pad movable between a disengaged position and a rear wheel braking position. The first hydraulic cylinder actuator includes a piston rod which extends from one end of the cylinder actuator and has an outer end connected to the rear brake pad. The system further includes a hydraulic cylinder device mounted on the frame adjacent the rear wheel and connected to the rear wheel braking mechanism so as to be operated thereby. This device is movable from an initial position corresponding to the disengaged position of the rear wheel braking mechanism to a secondary position when the rear wheel braking mechanism is in the rear wheel braking position. The hydraulic cylinder device extends at a substantial angle of more than 45 degrees to a longitudinal central axis of the first hydraulic cylinder actuator. A front hydraulic cylinder actuator mounted on the frame adjacent the front wheel is operatively connected to the hydraulic cylinder device so as to be actuated by movement of this device from its initial position to the secondary position. A front wheel braking device is connected to the front hydraulic cylinder actuator and is operable thereby during use of the brake system. This front wheel braking device is movable by the front hydraulic cylinder actuator between a non-braking position and a front wheel braking position. In operation of the system, the front wheel braking device brakes the front wheel when the rear wheel braking mechanism is in the rear wheel braking position.
Preferably the front wheel braking device is a front brake pad arranged to engage an outer circumferential surface of a tire of the front wheel.
Further features and advantages of this system will become apparent from the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings.